Besides microphones and loudspeakers, hearing aids also contain an amplifier circuit fitted with a volume control to adjust to individual needs. Push button switches electronically adjusting the volume in discrete steps already are known, however their ease of regulation is highly unsatisfactory.
Hearing aids of the above kind allow continual adjustment of the volume by rotating an adjustment wheel. This feature is more advantageous ergonomically and allows rapid coarse as well as fine adjustments. The design is widely used in hearing aids of all kinds.
However, in addition to volume control, hearing aids also require the setting of different operational modes, for instance when switching listening from the acoustic mode to an electromagnetic telephone receiver mode. For that purpose conventional hearing aids comprise additional switches reaching through the casing, as illustratively disclosed in U.S. Pat. No. 6,700,983 B1. Additional button switches however entail additional space requirements, raising problems for the very restricted space available in very small hearing aids. Moreover, additional switches do impair the aesthetics highly prized by aid wearers. Another problem in this respect is that operation by finger entails a minimum spacing between the volume control and the button switch in order to preclude simultaneously depressing the button switch when intending to adjust the volume control for instance. Typical finger size requires a spacing of about 10 mm (½ inch); as a result of the hearing aid's required minute size, considerable packing problems are then encountered.
The German patent document 3,503,390 A1 discloses a hearing aid where a push button switch to discretely adjust the volume is combined with a rotary switch to turn the aid ON/OFF. A similar compound switch is shown in the patent document WO 99/43193 combining a volume-changing push button switch with an ON/OFF slide switch.
The objective of the present invention is to create a hearing aid of the above species which shall be fitted with a compact and aesthetically acceptable switch.